The present invention relates generally to positioning controllers, and more particularly to a positioning controller for positioning a head at a starting position of an unrecorded region on a disk on which information is recorded by means of the sequentially inner-to-outer recording method or the sequentially outer-to-inner recording method.
The present invention is particularly applicable to write-once optical disk storages. The term "the sequentially inner-to-outer recording method", as used herein, means a method for recording information sequentially from the most inner track to the most outer track on the disk. And the term "the sequentially outer-to-inner recording method", as used herein, means a method for recording information sequentially from the most outer track to the most inner track on the disk. For example, a case where information is recorded on a file sequential-addressed by means of the ascending order or the descending order may be regarded as the sequentially inner-to-outer recording method or the sequentially outer-to-inner recording method. The term "write-once", as used herein, means a type of an optical disk unable to overwrite information at a predetermined region where other information has been recorded in advance. From this point of view, it differs from an erasable type of an optical disk which is able to overwrite the information at a predetermined region even if other information has been recorded thereon in advance.
In write-once optical disk storages, information is usually recorded by means of the sequentially inner-to-outer recording method. Before a plurality of information is recorded on the disk, for example, before second information is recorded, a last position of a recorded region of first information which is recorded just before the second information (the last position will be called "the last recorded position" hereafter) must be searched first of all. After searching the last position, then a head is moved to a position having an address next to an address of the last recorded position in order to record the second information. Hereupon, the address corresponding to the last recorded position will be defined as the last recorded address (called "LRA" for short), the address next to LRA will be defined as the recording start address (called "RSA" for short), and the position having RSA will be defined as the recording start position hereafter. Therefore, when arbitrary information is recorded on the disk, the last recorded position of information just prior to the arbitrary information must be searched in advance.
Among the methods of searching the last recorded position, the following method has been suggested. That is, an optical head is moved initially from the most inner track to the most outer track sequentially on a disk on which information is recorded by means of sequentially inner-to-outer recording method while reading a presence of recorded information thereof.
When the last recorded position is searched, LRA is stored in RAM (random access memory) as address information. Incidentally, RSA may be recorded in RAM instead of storing LRA. Thus when an attempt is made to record the next information, the head is positioned at a recording start position on the basis of the address information stored in RAM. Needless to say, the disk has been formatted so as to have address tracks on the whole recording surface thereof in advance.
However the above conventional method has the following disadvantages. It takes much time to search the last recorded position because the head must move and read the whole recorded region of the disk. Therefore, the broader the recorded region becomes, the more time it takes to search the last recorded position, and thus, much time is spent for the initial operation, so that information will not be recorded immediately.